The present invention relates to a hard disk drive system, in particular a micro-Winchester disk drive system.
With the rapidly expanding development of personal computers and desk top data processing systems, there has been a demand for increasing the performance of the disk drive systems of such computers. The major development in this direction has been the introduction of small Winchester disk drives as replacements and enhancements to floppy disk drives for program storage. The Winchester disk drive in general provides higher capacities and faster speeds of operation, factors which are important for the effective use of personal computers running advanced software packages.
The types of Winchester disk drives that have developed in this regard were originally based on the use of hard disks of diameter of approximately 51/2 inch, also known as mini-Winchester disks, and this so called "51/4 inch" disk drive has generally developed as an "industry standard." Such a Winchester disk drive can store typically 5-30 Megabytes of information when designed around an open-loop positioning system using a stepper motor capable of supporting up to approximately 360 data tracks per inch. However, advances made by the assignee of the present invention have expanded the storage capacity of the typical 51/4 inch disk drive up to 600 tracks per inch using this same basic type of open-loop positioning system, a track density previously believed not to be obtainable with such a stepper motor technology. Likewise, the assignee of the present invention has developed a 31/2 inch Winchester disk drive having 600 tracks per inch.
More recently, however, closed-loop positioning systems have been developed for use with 51/4 Winchester disk drives. Such drives typically use a linear voice coil motor to provide motive force for the actuator for positioning the heads over the appropriate tracks. Such closed-loop positioning systems are capable of achieving much higher numbers of data tracks per inch. For example, one such disk drive developed by the assignee of the present invention supports approximately 925 tracks per inch, with a resulting formatted storage capacity using a standard ST506/412 interface of approximately 5.3 Megabytes per disk surface. The positioning scheme of that disk drive is disclosed In the U.S. Pat. No. 4,638,384, issued Jan. 20, 1987.
With the introduction and popularity of portable personal computers, it is clearly a performance advantage if they can achieve a high degree of software compatibility with the desk top computing systems. Portability demands special requirements on the incorporation of a hard disk system, for example, light-weight, low power consumption and also the capability of withstanding harsher shock and vibration conditions. However, software compatibility also demands performance parameters such as data storage capability comparable to those available on 51/2 inch mini-Winchester disk drive systems.
As the software run on personal computers becomes more and more powerful and requires ever increasing amounts of media memory space, greater demand has been created for a micro-Winchester disk drive system having a large amount of data storage. Such disk drives are capable of storing such programs as well as providing fast access to the program and accompanying data for use by the central processing unit of the host microcomputer. At the same time, only a limited amount of physical space within the personal computer itself is required. A micro-Winchester disk drive typically measures 5.75".times.4.00".times.1.625" (1.times.w.times.h). The larger the storage capacity and the smaller the access time of the disk drive, the more complex and more powerful the software that can be run on that drive and the faster that program and its data can be accessed by the host computer.